A battery-less electrostimulator next to medicinal pills for size comparison. The new powering method allows the device to be wirelessly powered deep inside the body.
(Stanford University)

It’s time to throw out those bulky batteries.

Stanford researchers say they have developed a way to wirelessly transfer power to medical devices deep inside the body – a discovery that could lead to novel forms of pacemakers, nerve stimulators and other life-altering gadgets.

In a report published in the Proceedings of the National Academy of Sciences, lead researcher Ada Poon detailed how this technology could ultimately eliminate bulky batteries and recharging systems, paving the way for more compact medical devices.

And with this technique, the researchers note that doctors could soon treat more diseases with electronics rather than medications.

"We need to make these devices as small as possible to more easily implant them deep in the body and create new ways to treat illness and alleviate pain," Poon said.

The technology utilizes roughly the same type of wireless power transfer seen in cell phones, at levels that can safely penetrate deep inside the body. Poon made the engineering breakthrough when she figured out a way to blend two main types of electromagnetic waves – far-field waves and near-field waves.

Far-field waves can travel long distances, but when they encounter biological tissue, they are either reflected harmlessly or absorbed as heat, making them unsuitable for wireless medical devices. Comparatively, near-field waves have already been used in some types of wireless medical systems, but as their name implies, they can only transfer power over short distances.

By mixing the safety of near-field waves and the far-reaching capabilities of far-field waves, Poon was able to come up with a new type of electromagnetic wave that changed how it traveled when it moved from air to skin. She termed the resulting mixture “mid-field waves.”

Utilizing this new type of wave, Poon and her team created a pacemaker smaller than a grain of rice, which can be recharged wirelessly by holding a small power source above the device, outside the body. The researchers successfully tested it on a rabbit and are currently preparing the system for human use.

Poon and others hope that this discovery will spawn a new generation of microimplants, such as vital sensors, electrostimulators and even drug delivery systems that all can be powered from a wireless source.

"The Poon lab has solved a significant piece of the puzzle for safely powering implantable microdevices, paving the way for new innovation in this field,” said William Newsome, director of the Stanford Neurosciences Institute.